<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="root"></div>

    <script
      src="https://unpkg.com/react@18/umd/react.development.js"
      crossorigin
    ></script>
    <script
      src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"
      crossorigin
    ></script>
    <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>

    <script type="text/babel">
      const root = ReactDOM.createRoot(document.querySelector('#root'))

      class App extends React.Component {
        constructor() {
          super()

          this.state = {
            message: 'Hello World',

            isReady: true,

            info: {
              name: 'hxl',
              age: 18
            }
          }
        }

        render() {
          const { message, isReady, info } = this.state

          let showElement = null
          if (isReady) {
            showElement = <h2>准备好了</h2>
          } else {
            showElement = <h2>没准备好</h2>
          }

          return (
            <div>
              {/* 1.根据条件赋值给变量 */}
              <div>{showElement}</div>

              {/* 2.三元运算符 */}
              <div>{isReady ? <button>开始</button> : <h3>继续准备</h3>}</div>

              {/* 3.&&逻辑与 */}
              {/* 场景: 当某个值可能为false, 则需要 */}
              <div>{info && <h2>{info.name}</h2>}</div>
            </div>
          )
        }
      }

      root.render(<App />)
    </script>
  </body>
</html>
